For example, the existing patents such as patents with grant publication No. CN2922618 and No. CN102090805A disclose a reclining chair chassis; a chair made by such a chassis can recline during the use process, so that a person sitting on the chair feels more comfortable.
The Chinese patent with the granted publication No. CN2922618 and the filing date Jul. 17, 2006 discloses a lifting and reclining chair chassis, formed by an upper disc, a middle disc, and a knob. The knob is fixed on the upper disc by using a carriage bolt; a dust cover, a washer, and a spring are mounted on the middle disc, and U-shaped iron is disposed on the middle disc; a U-shaped support frame is connected to a back steel plate base and the upper disc; the back steel plate base is connected to the middle disc by using a rivet, and the U-shaped support frame is connected to the back steel plate base by using the rivet. A lifting pump is disposed on the middle disc. A lifting control switch is mounted on one side of the upper disc of the chair, and the upper disc is connected to the middle disc by using a rivet and a bearing. When the chair reclines, the spring performs a resetting function for reclining of the chair, and a resetting acting force of the spring on the reclining of the chair can be adjusted by adjusting an elastic acting force of the spring.
The Chinese patent with the granted publication No. CN102090805A and the filing date Dec. 10, 2009 discloses a chair chassis with adjustable reclining force, including a middle disc and a large disc. The rear part of the large disc can swing around a rotation shaft downward relative to the middle disc, and a knob disposed below a front part of the middle disc is provided with a cavity, a mounting plate fixed with the knob is disposed in the cavity of the knob; a worm wheel is disposed at a position, corresponding to the lower part of the mounting plate, of the knob, and the worm wheel can rotate around the axis of the worm wheel relative to the knob; a worm engaged with the worm wheel is disposed beside the worm wheel in the knob; one end of a handle extends into the knob from the outside of the knob and is in transmission connection with the worm; an adjustment bolt is in threaded connection with the worm wheel after passing through the large disc, the middle disc, and the mounting plate in the knob from top to bottom in sequence; the adjustment bolt is coaxial with the worm wheel, and a spiral spring is sleeved at a position, below the middle disc and above the mounting plate, of the adjustment bolt. By means of the transmission connection between the handle and the worm, handle rotation can drive worm transmission, and the worm drives rotation of the worm wheel; the worm wheel moves upwards or downwards along an axial direction of the adjustment bolt, so that the mounting plate mounted and fixed with the knob moves upwards or downwards to adjust a compression degree of the spiral spring, thereby implementing the objective of adjusting the reclining force of the spiral spring on the chair, during operation, a user only needs to stretch his hand to one side of the chair to hold the handle for rotation without bending over.
The foregoing two patents disclose two structures for adjusting resetting acting force, so that the magnitude of the resetting acting force can be adjusted when a person sits on a chair made of such a chassis, and therefor the chair can be adapted to use requirements of various populations. However, currently, there is no chair of which a chassis can select whether to have a reclining function according to a requirement of a user.